The present invention relates to a device for automatically changing reels of film, in particular stretch and/or shrink-wrap films, in machines which wrap products on pallets.
At present, one such machine for wrapping products comprises a frame which consists of a vertical column designed to support a ring, extending horizontally and mobile vertically in both directions, with a unit for wrapping products on pallets which are positioned at the base of the machine.
The ring moves vertically, surrounding the products so as to allow the unit to distribute the film completely around the products, thanks to the fact that it can rotate along the ring powered by relative drive means.
The wrapping unit basically comprises a support plate for a reel holder shaft, which turns freely, at least one pair of film pre-stretching rollers, one or more film feed rollers which guide it towards a so-called  less than  less than dandy greater than  greater than  roller (outside the wrapping unit), designed to allow the film to be distributed around the products correctly.
Such machines have proved highly productive in terms of time, but one of the operations which are relatively slow and, above all, difficult for machine operators is substituting the finished reel with a new reel. This is generally done manually by the operator who stops the machine, removes the cardboard core of the finished reel and fits a new reel on the shaft by inserting from the bottom upwards. The operator must then position the initial length of film along the path defined by the unit rollers as far as a gripper fixed to the ring, to allow initial film unwinding during the first few unit rotations along the ring.
Obviously, this operation is usually repeated several times in a short period, affecting the continuity of product wrapping, since lifting and positioning the new reels is difficult and time-consuming.
To reduce the reel change-over time, there is a device which is independent of the wrapping machine and consists of a carriage which moves towards and away from the ring. Said device is equipped with a sort of carrousel divided into two separate zones, the first with a wrapping unit complete with rollers and the new reel, and the second zone which is clear and ready to pick up the unit just used. In practice, when the reel on the machine finishes, the unit is stopped and the carriage brought under the unit fitted on the ring with the clear zone located below the unit; the ring is then lowered to allow the unit to rest on the carriage and detach from the ring. Following this operation, the carrousel is turned through 180xc2x0 so that the unit with the new reel is positioned below the support plate, to which the unit is then attached.
This device on one hand reduces the work of the machine operator, but on the other hand increases the cost of the machine, since at least one pair of (expensive) wrapping units is required for each machine. In addition, it should be considered that not all wrapping units have a simple structure and roller positioning which allows this type of automated solution.
The aim of the present invention is to eliminate this type of disadvantage, by providing a device for automatically changing reels of film for wrapping products extremely rapidly, which is reliable and relatively economical as a whole.